What is nitrogen dioxide?

The sum of nitric oxide (NO) and nitrogen dioxide (NO2) is commonly called nitrogen oxides (NOx). Other compounds, including nitrous acid and nitric acid, are part of the NOx family. NO2 is the component of greatest interest and the indicator for the larger group of NOx. NO2 forms quickly from emissions from cars, trucks and buses; power plants; and off-road equipment. In addition to contributing to the formation of ground-level ozone and fine-particle pollution, NO2 is associated with a number of adverse effects on the respiratory system.

Latest air quality planning that addresses the standard for nitrogen dioxide

On November 14, 2012, the commission adopted the Infrastructure and Transport SIP Revision for the 2010 NO2 NAAQS (Project No. 2012-016-SIP-NR). The SIP revision meets the infrastructure and transport requirements of the Federal Clean Air Act (FCAA), §110(a)(1) and (2) under the 2010 NO2 NAAQS. This revision documents how each infrastructure and transport element is currently addressed in the Texas SIP by outlining the requirements in FCAA, §110(a)(2)(A) through (M) and the Texas statutes and rules that allow Texas to meet each requirement.

The comment period was from June 29 through August 6, 2012. The United States Environmental Agency (EPA) submitted the only comments.

2010 One-Hour NO2 NAAQS

On February 9, 2010, the EPA published a final rule in the Federal Register to strengthen the primary NAAQS for nitrogen dioxide, establishing a new one-hour standard at 100 parts per billion (ppb). The new standard focuses on short-term exposures to NO2, which are generally highest on and near major roads. Currently, no area in Texas monitors above the 100 ppb standard. The EPA is retaining the current annual average NO2 standard of 53 ppb. The EPA is changing the monitoring network to capture both peak NO2 concentrations that occur near roadways and community-wide NO2 concentrations.

The EPA expects to decrease the number of new monitoring sites from the estimate provided in the 2010 rule. The EPA’s latest monitoring placement schedule addresses delays due to funding limitations. For Texas, near-road NO2 monitors in Dallas-Fort Worth (DFW), Houston-Galveston-Brazoria (HGB), Austin-Round Rock, and San Antonio areas are scheduled to be operational by January 1, 2014 with second monitors in DFW and HGB to be operational by January 1, 2015. El Paso and Edinburg-Mission-McAllen area monitors are scheduled to be operational by January 1, 2017. Once the expanded network of NO2 monitors is fully deployed and three years of air quality data have been collected, the EPA intends to redesignate areas based on data from the new monitoring network. The 2010 NO2 NAAQS attainment date is approximately five years after the date of nonattainment designations.

On February 17, 2012, the EPA published the final NO2 designations identifying all areas in the United States as unclassifiable/attainment (77 FR 9532) . The EPA administrator signed the initial designations on January 20, 2012 and sent a letter to the governor with the announcement.